Typewriter spacing selection and control mechanism

ABSTRACT

A typewriter has a printing head carriage mounted for movement along a rack having two toothings of different pitch, the carriage carrying two pawls each able to cooperate with a respective toothing. A slidable selector lever on the pawl, actuated by an universal bar, enables the selective engagement of one pawl with its rack and disengagement of the other. A second universal bar cooperates with the selected pawl to release it from the rack to control step-by-step movement of the carriage with a selected spacing.

United States Patent [1 1 Menzi [4 1 Oct. 14, 1975 TYPEWRITER SPACING SELECTION AND CONTROL MECHANISM [75] Inventor: Ulrich Menzi, Yverdon, Switzerland [73] Assignee: Hermes Precisa International S.A.,

Yverdon, Switzerland [22] Filed: Sept. 25, 1974 21 Appl. No.: 509,264

[30] I Foreign Application Priority Data Sept. 27, 1973 Switzerland 13830/73 [52] US. Cl. 197/84 R; 197/82 [51] Int. Cl. B41J 19/44 [58] Field of Search 197/82, 84 R, 84 B, 85,

[56] References Cited UNITED STATES PATENTS 1,857,771 10/1932 Trego 197/84 R FOREIGN PATENTS OR APPLICATIONS 233,985 4/1911 Germany 197/84 R 101,508 5/194] Sweden 197/84 R OTHER PUBLICATIONS IBM Customer Instruction Manual Form No. 241-56- 16-1 Reprint February 1972, Switch Pitch Operational Theory, pp. 138-142.

Primary ExaminerI-Iarland S. Skogquist Attorney, Agent, or FirmEmory L. Groff, Jr.

[57] ABSTRACT A typewriter has a printing head carriage mounted for movement along a rack having two toothings of different pitch, the carriage carrying two pawls each able to cooperate with a respective toothing. A slidable selector lever on the pawl, actuated by an universal bar, enables the selective engagement of one pawl with its rack and disengagement of the other. A second universal bar cooperates with the selected pawl to release it from the rack to control step-by-step movement of the carriage with a selected spacing.

5 Claims, 4 Drawing Figures US. Patent 0a. 14, 1975 l llllll TYPEWRITER SPACING SELECTION AND CONTROL MECHANISM I The invention relates to typewriters, notably of the type with a printing head comprising a carriage mounted for movement along a rack having first and second toothings of different pitch determining different spacing values for step-by-step movement of the carriage under the action of an elastic biasing force, and in particular to spacing selection and control mechanisms for such typewriters. 7

Known mechanism ofthis type have a pawl able to engage in one of the toothings, and means for temporarily disengaging the pawl. Several devices are also provided enabling, for example, the rack to be turned in a manner to place one of its toothings in front of the pawl mounted on the carriage. Such devices are relatively delicate to manipulate and lack precision.

The invention aims to remedy these drawbacks and to providea spacing selection and control mechanism of simpler and more robust construction, of which the majority of the elements may be provided on the carriage.

The spacing selection and control mechanism according to the invention comprises a first pawl able to engage in the first toothing, a second pawl able to engage in the second toothing, means for selectivelydisengaging either one of the pawls from its toothing, and a single control member controlling release from the rack of whichever pawl is not selectively disengaged.

The accompanying drawings show, schematically and by way of example, an embodiment of the invention. In the drawings:

FIG. 1 is a front elevational view of part of the mechanism; I

FIG. 2 is a view corresponding to Fig. 1,'showing an other position of operation of the mechanism;

Fig. 3 is an underneath overall plan view of the mechanism; and

Fig. 4 is a side elevational view along line lVIV of Fig. 2. The hereinafter-described spacing selection and control mechanism is' provided in a typewriter having a carriage l carrying a printing head 2, moving in the usual manner parallel to a platen cylinder, not shown. Movement of the carriage is actuated in known manner by the intermediary of a traction cable and control means, not shown. The carriage 1 moves in the proximity of and parallel to a rack 3 fixed on the frame of the machine. The rack 3 has two toothings 4 and 5 of different pitch, disposed side-by-side and whose teeth are directed downwardly. y

The spacing selection and control mechanism comprises a first pawl 6 pivotally mounted about a pin 7 rivetted on a wall 8 of carriage l. A second pawl 9, disposed parallel to pawl 6, is also pivotally mounted about the same pin 7. Each of these pawls 6, 9 is generally L-shaped and may pivot against 'the biasing action of a respective return spring 10, 11 attached to a part of the carriage l.

The horizontal arms of the pawls 6 and 9 have a catch 12, 13 respectively able to engage in arespective toothing 4, 5 of rack 3. The horizontal arm of the first pawl 6 is slightly longer than that of the second pawl 9, the ends of these arms being bent at right angles in a manner to form a transverse beak .14, 15 respectively. Each of these beaks 14, 15 is able to cooperate with an universal, spacing control bar 16 extending longitudinally 2 (i. e. parallel to the rack 3) and pivotally mounted on the frame of the machine.

The spacing selection and control mechanism also comprises a'selector lever 17 able to be slid vertically by the intermediary of means at the base of the carriage 1. This selector lever 17 is guided by a guide pin 18 fixed on plate'8 of carriage l and engaging in an elongated opening 19 in the selector lever. Vertical movement of the selector lever 17 is actuated by an universal bar 20 pivotally mounted on the frame of the machine and engaging in a groove 21 provided in a lug 22 situated towards the lower end of the selector lever 17 and protruding perpendicular to the plane thereof. At its upper end, the selector lever 17 is terminated by a beak 23 having two ramps 24 and 25 joined by a flat 26. The ramp 24 and flat 26 are both able to bear against a butt 27 at the lower end of the vertical arm of the first pawl 6. Also, the ramp 25 and flat 26 are both able to bear against a stud 28 provided at the lower end of the vertical arm of the second pawl 9, this arm being longer than the corresponding vertical arm of the first pawl 6.

The described mechanism operates in the following manner:

In the position shown in Fig. l, the selector lever 17 is held up by the universal bar 20. During upward movement to this position as indicated by arrow F, the flat 26 comes into contact with the butt 27 of the first pawl 6 which pivots about pin 7 in the clockwise direction, against the action of spring 10. The catch 12 of pawl 6 is thus disengaged from its toothing 4 of the rack 3. Moreover, the second pawl 9 is in a position with its catch 13 engaged in toothing 5, with the ramp 25 of the selectorlever l7 bearing againstthe stud 28 of pawl 9.

In the position shown in Figs. 2 and 4, the universal bar 20 holds the selector lever 17 down. During movement to this position, as indicated by arrow F', the butt 27 of the first pawl 6 slides along the ramp 24 and becomes completely disengaged from the beak 23 of selector 17. The pawl 6 is thus pivoted by the spring 10 in the counter-clockwise direction, so that its finger 12 engages in toothing 4. At the same time, the stud 28 of the second pawl 9 slides along ramp 25 and comes to The mechanism thus has two working positions, a single member, formed by the selector lever 17, enabling the selection at will of either one of the pawls 6, 9 to bring it to cooperate with the respective toothing 4 or 5 of the rack. When the carriage l is moved, the thusselected toothing determines the positions of the carriage 1 along the platen cylinder as a function of its pitch. Once the toothing has been selected, step-bystep movement of carriage 1 is controlled by the universal spacing control bar 16. This bar 16 is moved with a rapid downward movement in the direction of the arrow (Fig. 4), to bear on the beak 14 or 15 of the selected pawl, in a manner to release this pawl from the corresponding toothing, and thus allow movement of the carriage by one step.

It is noted that the pawls 6 and 9 are mounted with a slight play on pin 7, so as to permit a slight movement of these pawls at the moment when they come into engagement with their respective toothing. A slight play is also provided for the mounting of selector lever 17 on the guide pin 18.

It is thus seen that in the described mechanism, the rack 3 remains fixed and a single element (selector lever 17) enables disengagement of one pawl from one toothing and simultaneous engagement of the other pawl in the other toothing. It is also noted that apart from bars 17 and 20 all of the elements for control and selection of the spacing are disposed on the carriage l.

I claim:

1. In a typewriter comprising a carriage mounted for movement along a rack having first and second toothings of different pitch determining different spacing values for step-by-step movement of the carriage under the action of a biasing force, a spacing selection and control mechanism comprising a first pawl able to engage in the first toothing, a second pawl able to engage in the second toothing, means for selectively disengaging either one of the pawls from its toothing, and a single control member controlling release from the rack of whichever pawl is not selectively disengaged.

2. A typewriter spacing selection and control mechanism according to claim 1, in which said means for seiectively disengaging either pawl includes a single selection member slidably mounted on the carriage.

3. A typewriter spacing selection and control mechanism according to claim 2, in which the first and second pawls are both carried by the carriage.

4. A typewriter spacing selection and control mechanism according to claim 2, in which said single control member is an universal bar cooperating with transverse beaks of the pawls.

5. A typewriter spacing selection and a control mechanism according to a claim 2, in which said selection member has a beak having a first ramp cooperating with the first pawl and a second ramp cooperating with the second pawl. 

1. In a typewriter comprising a carriage mounted for movement along a rack having first and second toothings of different pitch determining different spacing values for step-by-step movement of the carriage under the action of a biasing force, a spacing selection and control mechanism comprising a first pawl able to engage in the first toothing, a second pawl able to engage in the second toothing, means for selectively disengaging either one of the pawls from its toothing, and a single control member controlling release from the rack of whichever pawl is not selectively disengaged.
 2. A typewriter spacing selection and control mechanism according to claim 1, in which said means for selectively disengaging either pawl includes a single selection member slidably mounted on the carriage.
 3. A typewriter spacing selection and control mechanism according to claim 2, in which the first and second pawls are both carried by the carriage.
 4. A typewriter spacing selection and control mechanism according to claim 2, in which said single control member is an universal bar cooperating with transverse beaks of the pawls.
 5. A typewriter spacing selection and a control mechanism according to a claim 2, in which said selection member has a beak having a first ramp cooperating with the first pawl and a second ramp cooperating with the second pawl. 